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1. Field of the Invention
The invention relates generally to the field of computer networking devices. More particularly, the invention relates to a Gigabit media access controller (GMAC) having support for redundant physical links.
2. Background Information
With Local Area Network (LAN) switches now operating at data transfer rates of up to 1 Gigabit per second (Gbps), switch-over from a failed physical link to another physical link is of critical importance.
As used herein, the terms Ethernet, Fast Ethernet, and Gigabit Ethernet shall apply to Local Area Networks (LANs) employing Carrier Sense, Multiple Access with Collision Detection (CSMA/CD) as the medium access method, generally operating at a signaling rate of 10 Megabits per second (Mbps), 100 Mbps, and 1,000 Mbps, respectively over various media types and transmitting Ethernet formatted or Institute of Electrical and Electronic Engineers (IEEE) standard 802.3 formatted data packets.
In the prior art there are methods and systems which support redundancy of signals, however, the switch-over from the failed data stream to the redundant data stream in the prior methods and systems tend to have a long latency.
In one prior art switch system two media access controllers (MACs) are used to create a redundancy of signals between the switch and the respective source and/or destination port. FIG. 1 illustrates a switch 150 that uses two MACs 160 and 165 to create redundant links between the switch 150 and at least one of input/output (I/O) devices 101-104. One of the MACs 160 and 165 is the primary MAC and the other is the redundant (or backup) MAC. Both MACs 160 and 165 set up links to the desired source and/or destination port, here one of the I/O devices 101-104. For the sake of an example, MAC 160 sets up a primary link to I/O device 102 and MAC 165 sets up the redundant link to the same I/O device 102. While MAC 160 communicates with I/O device 102 along the primary link, the redundant link remains idle with no communication between MAC 165 and I/O device 102.
However, when a link failure or interrupt occurs along the primary link, the system must switch over to the redundant (or backup) link. For the purposes of the example given above, this means that the system must shut down (or set to idle) the primary link between primary MAC 160 and I/O device 102 and switch over to the redundant link between the redundant MAC 165 and I/O device 102. This xe2x80x9cswitch-overxe2x80x9d is sometimes done using a software algorithm, for example Spanning Tree Protocol, which takes a long time, i.e. a few to several seconds, to switch from the broken or interrupted link to the redundant or backup link. On a high-speed link, such as a Gigabit Ethernet, a few to several seconds may equate to a large amount of traffic lost at the core of the enterprise network.
Thus, what is needed is a method and system for supporting redundant links with fast switch-over times.
A method and apparatus for a media access controller supporting redundant links are described. According to one aspect of the present invention a media access controller includes a two transceivers for communication with an source and/or destination port. Each transceiver has a receiver and transmitter. When the media access controller sets up a physical link to the desired source and/or destination port each transceiver sets up a separate physical link to the source and/or destination port. One of the physical links is the primary physical link and the other is a redundant or backup physical link. By using two physical links if a failure of interrupt occurs on the primary physical link then a switch-over is performed to use the redundant physical link.
Additional features and benefits of the present invention will become apparent from the detailed description, figures, and claims set forth below.